1. Field of the Invention
The present invention relates to a fluid control valve for controlling a fluid flow of large flow rate, such as that used in a fluid pressure elevator to supply a high pressure fluid to, and discharge it from, a fluid pressure jack to raise or lower the cage of the elevator.
2. Prior Art
As described in the Publication "Hydraulic pressure and pneumatic pressure" from Institute of Hydraulic and Pneumatic Engineering, May 1986, Vol. 17, No. 3, pages 181-186, conventional flow control valves of this type have ports respectively communicating with a pump fluid pressure cylinder and with a tank, and also have hermetic fluid control parts each between a pump port and a fluid pressure cylinder port and between the fluid pressure cylinder port and a tank port. These fluid control parts use a pilot valve to control the fluid.
The above-mentioned type fluid control valves are complicated in structure, because they are intended to achieve a high precision flow rate control, which is the inherent object of the fluid control valves, while ensuring a hermetic seal to keep the fluid pressure cylinder at rest. Further, in controlling the fluid, they will cause cavitation, producing large noises, because they will execute the flow-rate control of the high pressure fluid.